A problem which occurs with fluid filter assemblies, particularly useful for diesel engines and gasoline marine engines, is facilitating the removal of contaminants from the filter assembly. These contaminants include water and particulate matter which tend to settle at the bottom of housings used to retain filter elements. In order to remove the water and particulate matter suspended in the water, drain valves are frequently positioned at the bottom of housings used to retain filter elements. If a simple drain cock is utilized for the valve, the drainage may not be complete or may not occur at all because a partial vacuum is created in the filter housing upon initiating drainage. The partial vacuum prevents water from flowing through the open valve.
In order to facilitate drainage by breaking the partial vacuum, drainage valves in fuel filters are vented. It is necessary to close the vent hole when the valves are closed so that fluid within the fluid filter does not flow out through the vent hole. In prior art arrangements, there is the possibility of vent holes becoming blocked by particulate debris suspended in the fuel or water at the bottom of the housing. This is because the end of the vent tube, which opens within the housing, is left continuously open so that over time particles can accumulate in the vent tube.
In addition to improving the reliability of self-venting valves by having valves which are less likely to have clogged vent tubes, it is also desirable to have a valve which is relatively easy to retrofit and install in existing fuel filter assemblies without extensive modification of those assemblies.